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# Internal resistance question. Help! watch

1. The pd across the terminals of a battery is found to be 3V when it is measured using a very high resistance voltmeter. The battery is then connected to a 10 ohm resistor and its terminal pd drops to 2.8V. Calculate the internal resistance of the battery.
The pd across the terminals of a battery is found to be 3V when it is measured using a very high resistance voltmeter. The battery is then connected to a 10 ohm resistor and its terminal pd drops to 2.8V. Calculate the internal resistance of the battery.
Total supply (E) is going to be?
What will the current in the circuit be, algebraically?
Ohm's Law across the resistor
Solve
3. All that you need to solve this is the formula E = I(R + r), where E is the e.m.f., I is the current, R is the resistance, and r is the internal resistance.

Tip:
Expanding the brackets will give you E = IR + Ir.
IR is the terminal potential difference and Ir is the lost volts.

Good luck!

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